Method and apparatus for drilling wells with eccentric jet drills



Dec. 31, 1968 G. H. F. GARDNER 3,419,091 METHOD AND APPARATUS FOR DRILLING WELLS WITH ECCENTRIC JET DRILLS Sheet Filed March 30, 1967 INVENTOR.

Dec. 31, 1968 G. H. F. GARDNER 3,419,091

METHOD AND APPARATUS FOR DRILLING WELLS WITH ECCENTRIC JET DRILLS Filed March 30, 1967 Sheet 3' of 3 fllll ll I. 9 A} A a i; I/ /86 in II I \fliv/ ZOC NH I $7226 E; r.

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| 9 6540 b. GARDNER 3,412,921 METHOD AND APPARATUS FDR DRILLENG WELLS WITH Et'JCENTRlC JET DRILLS Gerald H. F. Gardner, Pittsburgh, Pa, assignor to Gulf Research Develepment Company, Pittsburgh, Pa, a

corporation of Delaware Filed Mar. 30, 1967, Ser. No. 627,232 19 Claims. (Cl. 175-67) ABSTRACT 6F THE DESCLQSURE Method and apparatus for drilling earth boreholes by means of high pressure jets of an abrasive-laden slurry wherein the drill head is substantially smaller than the diameter of the hole, is mounted off-center with respect to the axis of the hole, and is caused to rotate eccentrically within the hole.

This invention pertains to drilling wells in the earth by means of high velocity jets of an abrasive-laden slurry and an eccentric drill. The invention comprises drill heads which are considerably smaller than the diameter of the hole being drilled. The drill head, and the drill pipe carrying the drill head, is mounted in the drill olfcenter or eccentrically with respect to the axis of the hole, and means are provided to cause the nozzle or nozzles to traverse the entire bottom of the hole. By using a drill head considerably smaller than the diameter of the hole, as opposed to a drill bit in which the cross-sectional area is substantially equal to or at least of the same orders of magnitude as the borehole, fewer but larger nozzles can be used. The use of larger nozzles permits the use of larger abrasive particles in the drilling slurry which it is anticipated will result in increased drilling rate.

The use of a smaller number of larger nozzles permits a higher jet velocity using a smaller volumetric flow through the drill pipe. That is, for any given power input at the surface, a smaller number of larger nozzles will produce a higher jet velocity and a lower volumetric flow rate through the drill pipe than would a larger number of smaller nozzles. The greater volume of formation removed by the higher jet velocity more than compensates for the smaller number of nozzles. Lessening the volumetric flow rate through the drill pipe lowers the friction loss in the drill pipe, and hence increases the efficiency of transfer of power from the surface pumps to the nozzles. This benefit increases with depth because of the increased length of drill pipe.

If carried to its logical end, a drill with only one nozzle would be provided. A problem in drilling a relatively large hole with one nozzle is the provision of a substantially uniform removal rate all over the bottom of the hole. In those embodiments of the present invention in which the nozzles are moved eccentrically over the bottom of the borehole, a single nozzle as well as a plurality of nozzles may be provided. Hence, the present invention encompasses an eccentric drill having only one nozzle.

In the accompanying drawing forming a part of this disclosure, FIG. 1 is a vertical, sectional view of a first embodiment of a drill embodying the invention; FIG. 2 is a cross-sectional view taken on line 22 of FIG. 1; FIG. 3 is a partial bottom plan view of a portion of the drill of FIG. 1 taken on line 3-3 thereof; FIG. 4 is a view similar to FIG. 1 showing a second embodiment; FIG. 5 is a bottom plan view taken along line 5-5 of FIG. 4; FIG. 6 is a view similar to FIG. 1 showing a third embodiment; FIG. 7 is a partial bottom plan view ill taken along line 77 of FIG. 6; FIG. 8 is a View similar to FIG. 1 of a fourth embodiment; and FIG. 9 is a bottom plan view taken along line 99 of FIG. 8.

Referring now in detail to the drawing, a first embodiment of the apparatus of the invention is shown in FIGS. 1 through 3, and comprises a drill 10. Drill 10 is removably mounted on the lower end of a drill string 12 by any conventional connector means 14, and comprises a main drill body 16. Drill body 16 is formed with an oif-center longitudinal through opening 18 to permit the return flow of the drilling fluid, abrasives, and cuttings back to the surface. Body 16 is formed with a second longitudinal through opening 20, in which is mounted a drill stem member 22 by means of bearing 23. The upper end of drill stem 22 is formed with an upper stop flange 24 which has an outside diameter larger than the diameter of opening to prevent downward movement of stem 22 with respect to body 16. The upper extension 26 of drill stem 22 is joined to drill string 12 by means of connector 14. The lower end of drill stem 22 is formed into a drill head 28. It will be apparent that drill head 28 could be also formed as a separate member and joined to the drill stem by conventional means.

Drill head 28 comprises an upper surface 30 which is in closely spaced relation to the undersurface of a bottom plate 32 on the undersurface of body 16. Thus, surface 30 and flange 24 prevent any substantial relative motion between body 15 and drill stem 22, and hold body 16 and stem 22 together. Drill head 28 comprises an internal slurry receiving chamber 34. At least one nozzle 36 extends through the bottom portion 38 of drill head 28 and is in fluid communication with chamber 34. As shown in FIG. 3, drill head 28 carries three nozzles, but a single nozzle could be provided if desired. Drill head 28 is also provided with a stand-off bar 40 of hard abrasion resistant material such as tungsten carbide which rides against the bottom surface of the borehole to maintain the stand-ofi" of the exit end of the nozzle or nozzles from the borehole bottom, and also serves to physically break 0d any minor ridges which may remain between the grooves cut by the abrasive slurry.

Means are provided to transform the rotation of the drill string 12 about its own axis imparted to it by the conventional rotary drilling equipment at the surface (not shown) into simultaneous rotation of drill head 28 about both the axis of drill stem 22 and the axis of drill 10. The axis of drill 10 will substantially coincide with the axis of the hole being drilled. To this end, a fixed housing 42 is provided, and comprises a plurality of bow type centralizer springs 44 which cooperate with the side wall of the borehole to hold housing 42 stationary as to rotation in the borehole with respect to its own axis. The springs 44 will permit the drill 1G to move axially in the borehole, as is well known. Housing 42 comprises a housing body comprising a thickened central portion 46 and a pair of flange portions 48 extending outwardly from the outside of thickened central ortion 46. The body of housing 42 fits within a suitably formed opening 50 formed in body 16. Suitable bearings 52 are provided to permit rotation of drill body 1d with respect to fixed housing 42, and sealing means 54, such as O-rings or the like, are provided to prevent the flow of any well fluids into the joints and bearings.

The body of housing 42 is a ring-like member and encircles the drill 10 within its opening 50, so that drill 10 has a smooth outer surface, except for springs 44. The inside cylindrical surface of central portion 46 is formed with gear teeth 56. As is shown in FIG. 2, drill stem 22 is positioned within body 16 so that it is close to the plane of the surface carrying gear teeth 56. A portion of drill stem 22 is formed with gear teeth 58 which mate with gear teeth 56.

The upper end of drill 1G is shown broken in FIG. 1. The length of the drill will be determined by the weight required for efiicient drilling, and it will be understood that if needed, another member like housing 42 may be provided for added stability and to insure smooth operation.

The kinetic relationship between drill stem 22 and thickened portion 46 is that of a planetary/sun gear arrangement, with thickened portion 46 comprising the fixed sun gear. As is well known, by suitable selection of the number of gear teeth 56 and 58, a relationship can be created that will insure that the nozzle or nozzles 36 will be in a different position each time they come to any one reference position with respect to housing 42. Thus, each nozzle will describe a path on the borehole bottom which will have the geometric configuration of a generalized hypocycloid.

Referring now to FIGS. 4 and 5, there is shown a secnd embodiment 60 of the apparatus of the invention. Drill 60 is adapted to cut cores as it drills. Parts similar to those described above in regard to drill it}, are indicated by the same reference numerals followed by an a.

The lower end of drill 60 differs from the lower end of drill 10. A drill head 62 is provided in place of drill head 28 and comprises a slurry receiving chamber 64. The bottom wall portion 66 of drill head 62 is provided with a plurality of nozzles 36a. Drill 60 comprises a thickened bottom closure plate portion 68. As shown in FIG. 5, bottom plate portion 68 carries a stand-off bar 70 positioned opposite drill head 62. Bottom plate portion 68 is formed with a core chamber 72 which is cylindrical and coaxial with the axis of the drill. A pair of fluid return passages 74 are formed in bottom plate 68 to comn municate the space below the drill with fluid return hole 18a.

As drill 60 is operated, a cylinder of material will be continuously formed in core chamber 72 and will periodically break off due to vibrations of the drill. The cores will be carried up to the surface with the return flow in passage 18a.

Referring now to FIGS. 6 and 7, there is shown a third embodiment 76 of the apparatus of the invention. Drill 76 incorporates the feature of a retrievable nozzle. That is, with drill 7 6 it is possible to remove and replace only the nozzles without pulling the drill and drill string out of the borehole. Parts similar to those described above in regard to drill 10, are indicated by the same reference numerals followed by a b.

The lower end of drill 76 is provided with a drill head 78, which comprises a bottom plate portion 80 formed with a nonround opening 82 in which is seated a drill holder 84 having an external configuration to fit snugly within opening 82. Bottom plate 80 is also formed with a pair of inwardly extending lugs 86 that fit within suitably formed slots in the side of holder 84, to prevent holder 84 from falling out downwardly of the drill head 78. The upper surface of holder 84 is provided with a device 88, such as a handle or latch, which is adapted to cooperate with a suitable fishing tool. Thus, a wire line can be dropped down the inside of the drill string and drill stem 22b to grasp holder 84 by latch or handle 88 to pull the holder and its nozzles 32b out of the hole for replacement of the nozzles on the surface. The nonround shape and the lugs 86 assure proper seating of the holder in drill head 78 and also prevent any relative rotational motion in a horizontal plane between the drill head and the nozzle holder.

Referring now to FIGS. 8 and 9, there is shown a fourth embodiment 90 of the apparatus of the invention. Drill 90 is a modification of the apparatus of the invention wherein the rotation of the drill string around its own axis imparted to it by the rotary equipment at the surface is wholly transformed into rotation of the drill stem about the axis of the drill. Parts similar to those described above in regard to drill 10 are indicated by the same reference numerals followed by a c.

In drill 90 flange 24 is omitted and drill stem 220 is fixed with relation to opening 200 by any suitable means such as welding. Nothing equivalent to gear teeth 56 and 58 of drill 10 are used in drill 90.

A drill head 92 is provided and comprises a bottom plate portion 94 provided with a stand-off bar 96 and a plurality of nozzles 360. As shown in FIG. 9, the diameter of drill head 92 is at least equal to and preferably slightly larger than the radius of drill 90. Since the drill head 92 does not rotate about the axis of drill stem 220, the pattern cut in the bottom of the borehole by the nozzles 360 will comprise a plurality of concentric circles. Therefore, the nozzles 36c are positioned in bottom plate 94 at appropriate radii and appropriate angles to leave a minimum amount of the formation between them to be broken off by stand-off bar 96.

As will be clear to one skilled in this art, the four drill heads described, 28, 62, 78 and 92 are substantially interchangeable as shown, and fully interchangeable with only minor changes. For example, drill head 78 could be used in place of drill head 28 or 62 with only an adjustment of dimensions to assure that the retrievable holder 84 reaches out to the outside of the borehole.

While the invention has been described in detail above, it is to be understood that this detailed description is by way of example only, and the protection granted is to be limited only within the spirit of the invetnion and the scope of the following claims.

I claim:

1. A method of drilling earth boreholes by the use of a high velocity jet of an abrasive-laden slurry, rotary surface drilling equipment, and a drill string; comprising the steps of mounting a slurry jetting means in a drilling head having the diameter equal to about half the diameter of the hole being drilled, and transforming the rotation of the drill string about its own axis imparted to it by the surface rotary drilling equipment into rotation of said drill head about the axis of the borehole.

2. The method of claim 1, and transforming the rotation of the drill string about its own axis imparted to it by the surface rotary drilling equipment into simultaneous rotation of said drill head about the axis of the drill string and the axis of the borehole.

3. A method of drilling earth boreholes by the use of a high velocity jet of an abrasive-laden slurry, comprising the steps of mounting a slurry jetting means eccentrically with respect to the axis of the hole being drilled, rotating said jetting means about a first axis, positioning said first axis off-center with respect to the axis of the borehole, and rotating said first axis about the axis of the borehole simultaneously with the rotation of said jetting means about said first axis.

4. Apparatus for drilling earth boreholes by means of a high velocity jet of an abrasive-laden slurry comprising a drill string, a drill at the lower end of said drill string, means at the surface to impart rotary motion to said drill string about its own axis, said drill comprising a drill stem, means to connect the upper end of said drill stem to the lower end of said drill string, a drill head at the lower end of said drill stem, said drill head having a largest dimension parallel to the plane of the bottom of the borehole equal to about half the diameter of the borehole being drilled, said drill head comprising a nozzle communicating the inside of said drill stem with the space below said drill, said drill being formed with a longitudinal return opening extending through the lentgh thereof and communicating the space below said drill with the space above said drill, the axis of said drill stern being parallel and offset from the axis of said drill, said drill comprising a portion adapted to be fixed to the wall of the borehole against rotation about the axis of the drill and to permit motion of said drill along the axis of said drill, and means to permit rotation of said drill stem on said fixed portion about the axis of said drill.

5. The combination of claim 4, said rotation permitting means further comprising means cooperative with a portion of said drill stem to cause said drill stem to rotate about its own axis simultaneously with its rotation about the axis of the drill.

6. The combination of claim 5, said cooperating means comprising gear teeth formed on a portion of the outside of said drill stem and mating gear teeth formed on the inside surface of said fixed portion.

7. The combination of claim 4, said drill head comprising a nozzle holder removably seated therein, said nozzle being mounted in said nozzle holder, and said nozzle holder comprising means to permit the removal of said nozzle holder by the use of a wire line passing through the inside of said drill string-and said drill stem, whereby said nozzle may be retrieved or replaced without removing said drill string and said drill from the borehole.

8. The combination of claim 5, said drill head comprising a' nozzle holder removably seated therein, said nozzle being mounted in said nozzle holder, and said nozzle holder comprising means to permit the removal of said nozzle holder by the use of a wire line passing through the inside of said drill string and said drill stem, whereby said nozzle may be retrieved or replaced without removing said drill string and said drill from the borehole.

9. The combination of claim 8, said nozzle holder comprising a nonround, transverse cross-sectional shape, said drill head being formed with an opening having a crosssectional shape adapted to make with the shape of said nozzle holder, and said nozzle holder and drill head comprising means to prevent said n'OZZle holder from moving downwardly with respect to said drill.

10. The combination of claim 4, said drill comprising a bottom plate member coplanar with said drill head, whereby said bottom member and said drill head substantially close off the bottom end of said drill; said bottom member being formed with an axial cylindrical opening coaxial with the axis of the drill, said axial cylindrical opening communicating the space below said drill with said longitudinal return opening, whereby said drill will cut a core of the formation being drilled.

11. The combination of claim 5, said drill comprising a bottom plate member coplanar with said drill head, whereby said bottom member and said drill head substantially close off the bottom end of said drill; said bottom member being formed with an axial cylindrical opening coaxial with the axis of the drill, said axial cylindrical opening communicating the space below said drill with said longitudinal return opening, whereby said drill will cut a core of the formation being drilled.

12. The combination of claim 10, said bottom plate member being provided with a stand-off bar of hard abrasion resistant material extending down below the lowermost surface of said bottom plate member and said drill 'head, and said stand-off bar being positioned on the 6 opposite side of said axial cylindrical opening from said drill head.

13. The combination of claim 4, said drill comprising an elongated cylindrical drill body, said portion fixed against rotation about the axis of the drill comprising a fixed housing, said fixed housing having an outer cylindrical surface substantially coplanar with the outer cylindrical surface of said body, rotary fluid sealing means between said fixed housing and said drill body, sealing means between said fixed housing and said drill body, and said fixed housing comprising a plurality of bow springs extending outwardly from the outer cylindrical surface of said fixed housing and adapted to engage the side wall of the borehole.

14. The combination of claim 4, said drill head comprising a stand-01f bar of hard abrasion resistant material extending down below the lowermost surface of said dn'll head.

15. The combination of claim 4, the bottom surface of said drill being provided with a bottom plate member of hard abrasion resistant material, the upper surface of said drill head being positioned in closely spaced relation to the bottom surface of said bottom plate member.

16. The combination of claim 4, said drill stem comprising flange means extending outwardly from the outer surface thereof in closely spaced relation to the upper surface of said drill, whereby said drill is constrained against upward axial motion along said drill stem.

17. The combination of claim 5, said drill head comprising a single nozzle, and said rotation permitting means and said cooperating means being adapted to cause the jet from said single nozzle to cover substantially the entire bottom surface of the borehole.

18. The combination of claim 17, said drill head comprising a stand-off bar of hard abrasion resistant material extending down below the lowermost surface of said drill head.

19. The combination of claim 4, said drill head comprising a plurality of said nozzles, and said drill head comprising a stand-off bar of hard abrasion resistant material extending down below the lowermost surface of said drill head.

References Cited NILE C. BYERS, JR., Primary Examiner.

US. Cl. X.R. 3l9, 399

Stark 175-67 X 

